The present invention relates to a running resistance detecting apparatus for a vehicle, which apparatus is capable of detecting a running resistance of an automobile without being affected by running conditions thereof.
In a conventional control apparatus for altering a control method or mode as well as control parameters involved in controlling operations of a motor vehicle, the control constants are altered or changed in accordance with the running resistance previously determined on the basis of speed data obtained for the running on a level road or in fluordance with the amount a throttle valve is opened for the purpose of coping with an increase in the running resistance, which can occur during uphill driving. In another known apparatus, the resistance value previously determined on the basis of the degree of opening of the throttle and the vehicle speed at the time when acceleration is zero is corrected as a function of the change in the acceleration, as is disclosed in Japanese Patent Application No. 63-144367.
As understood from the above, in the apparatus known heretofore, the running resistance which the motor vehicle is subjected to in uphill driving or upon acceleration is estimated simply on the basis of the vehicle speed and the throttle opening degree. However, it has been round difficult to determine the running resistance with any satisfactory accuracy using only these parameters. On the other hand, determination of the running resistance in the state in which the acceleration is zero is subjected to severe limitations because such a state only rarely occurs.
Such being the circumstance, an the apparatus, such as a cruise control apparatus controlled by the known running resistance detecting means, suffers from a problem that a control gain changes significantly in uphill/downhill running, resulting in a repetition of acceleration and deceleration and hence unwanted hunting, because the running resistance is determined on the basis of the speed of the motor vehicle running on a level road. Further, it is noted that in an engine including an automatic transmission or the like, the running state or mode is controlled by altering related control constants through manual operation of a relevant switch by the driver, which means that a burden imposed on the driver increases or acceleration performance is degraded when the switch manipulation is neglected.